Without presence of tubing, cement bonds behind casing has proven able to be evaluated by acoustic methods such as sonic cement bond logging, the ultrasonic pulse-echo method, and the pitch-catch method. However, there is no reported acoustic method effective to estimating cement bonds through tubing. Through-tubing cement bond evaluation becomes a challenge because of the unwanted strong interference of tubing.

Here, we propose a novel acoustic method for through-tubing cement bond evaluation based on low-frequency Mie resonances excited by cylindrical wavefronts. Physically, the phenomenal Mie and the companied anti- resonances can be explained by the coupling Duffing model. This model shows that the change of cement impedance can be characterized by the response change of Mie resonances. The amplitude of Mie resonances at low frequencies has an appreciable response even though there exists tubing. Then, the response is qualitatively captured by the change of the electrical input power fed to the cylindrical transducer, based on the principle of acoustic Purcell effect. Therefore, by measuring the electrical input power or terminal resistance, cement bonds can be evaluated through tubing. Last but not least, our proposed method has the capability of not only evaluating cement bonds but also estimating the quantity of casings and the eccentering of tubing based on the azimuthal profile of Mie resonances.

Introduction

Production logging requires cement monitoring with the existence of tubing. When pressure imbalance causes crossflow through poorly cemented sections, excessive production of unwanted fluids might occur. There is a highly demand for a solution of cement bond logging through tubing to save time and money. Not only in the area of production logging, the operation of well abandonment is also eager for the technique of cement bond logging through tubing. A well that comes close to the end of its operating life cycle requires to be plugged and abandoned (P&A). One possible way to cut the costs during P&A operations is to leave most of the production tubing in wells so that the rig time and money could be significantly reduced. As an important preparation task for P&A operations, well integrity such as cement bond condition behind casing needs to be tested beforehand.

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